The invention relates to a process for the preparation of fine-particled, stable, pharmaceutical or cosmetic dispersions consisting of an aqueous phase and an organic phase which is insoluble or not completely soluble in water (oily phase), in which a pre-emulsion is first prepared from the two phases by known emulsifying methods and is then further processed to the end product. The invention furthermore relates to apparatus for carrying out the process.
Pharmaceutical or cosmetic emulsions are usually prepared by combining, at a temperature of 60.degree. to 80.degree. C., the molten organic phase (oily phase) and the entire aqueous phase, which has been brought to the same temperature, in a stirred kettle and, in the case of ointments and creams, cooling the mixture to room temperature in an ointment reactor with stirring and homogenising tools and thereby homogenising it. In the case of emulsions which are capable of flowing, the crude emulsion thus obtained is pre-emulsified, cooled to 20.degree. to 40.degree. C. in a jacketed or flow-through cooler and then very finely dispersed with a hig-pressure homogeniser. A disadvantage in this type of preparation of an emulsion which is capable of flowing is that the entire batch must first be heated up and then cooled again, after pre-emulsification, in order to bring the entire emulsion to the desired fineness with frequently only a small amount of disperse oily phase by means of high-pressure homogenisers. High-pressure homogenisers require a very high operating pressure in the order of size of 200 bar, which can only be produced with relatively expensive multistage high-pressure piston pumps of high power. Moreover, the temperature programme described above, necessitated by the technology, gives rise to a high energy consumption.
A further disadvantage is that high-molecular organic compounds may be destroyed by the high shearing forces in the high-pressure homogeniser, so that damage to the product occurs.
Expensive ointment reactors (heavy machine columns, vacuum devices, complicated shaft packing and the like) in which completely undefined preparation conditions prevail as a result of simultaneous stirring, homogenising and cooling (for example each volume element of the product will pass through the shearing gap of the homogeniser only on a statistical average basis) have hitherto been used for the preparation of ointment and cream products. Moreover, poor heat transfer gives rise to long cooling times.